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Space Telescope Imaging Spectrograph
STAN - Feb 2010

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| STScI Analysis Newsletter (STAN)
| Space Telescope Imaging Spectrograph (STIS)
| February 2010
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Visit the "New in the Last 45 Days" section of the STIS website at http://www.stsci.edu/hst/stis for new information about STIS.

This and previous issues of the STAN can be found at http://www.stsci.edu/hst/stis/documents/newsletters.

CONTENTS:

STIS INSTRUMENT:

-Update on STIS NUV MAMA Dark Current

-New pixel-to-pixel Flat Fields for STIS CCD Spectroscopy

STIS DOCUMENTATION AND USER SUPPORT UPDATES:

-STIS Calibration Posters Presented at 215th AAS Meeting

-Recent STIS Instrument Science Reports

-Updates to STIS Web Pages

-New ETC Special Notices Page

-IHB Errata

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Update on STIS NUV MAMA Dark Current

After SM4, the STIS NUV MAMA dark current was found to be about 10 times higher than had been expected. This excess dark current has been slowly decreasing with a time scale of about 110 days. As of mid-January 2010, the mean level was about 0.005 counts/pixel/s (about 5200 counts/s over the entire detector). This is still about 4 times higher than the levels seen in 2003 and 2004. While we hope that the dark current will continue to decline, we cannot guarantee it, because the physics behind the excess dark current is not well understood. For cycle 18 exposure estimates, users should continue to adopt the rate of 0.005 counts/pixel/s that is currently implemented in version 18 of the STIS Exposure Time Calculators. For further discussion of the NUV MAMA dark current, see Section 7.5.2 of the STIS IHB.

New pixel-to-pixel flat fields for STIS CCD Spectroscopy

New pixel-to-pixel flat fields for all STIS CCD spectroscopic modes were delivered on Dec 17, 2009. These flats are based on post-repair tungsten lamp observations and should improve the limiting S/N for any STIS CCD spectroscopic observation taken since STIS was repaired. Use of the new flats is especially recommended for data with sufficient counts to support S/N > 100:1 per pixel. Users can automatically recalibrate such data with the new reference files by retrieving them from the archive.

STIS Calibration Posters Presented at 215th AAS Meeting

A number of posters presenting post-SM4 STIS instrument performance information were presented on January 5, 2010, at the 215th AAS meeting in Washington DC. The titles and links to copies of the STIS posters can be found here.

Recent STIS Instrument Science Reports

A number of new STIS ISRs have been prepared summarizing results from SMOV and early Cycle 17 calibration observations. These can provide useful information for interpretation and planning of STIS observations.

Updates to STIS Web Pages

Since the release of the new STIS Instrument Handbook, we have completed a review of the STIS web pages. As part of this review, a number of links into the IHBs were corrected and revised to conform with the Cycle 18 versions. If you find any additional links which are broken or which appear to be misdirected, please forward your concern to help@stsci.edu so we can both point you to the correct information and fix any remaining errors on these pages.

New ETC Issues page

Reports of bugs and other special notices relevant to the use of the Cycle 18 Exposure Time Calculators (ETCs) will be posted at http://www.stsci.edu/hst/observatory/etcs/release_notes.

IHB Errata

A list of the current errata for the STIS Instrument Handbook.

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